Pat steak cubes dry and season with salt and pepper.
Heat olive oil and 2 tbsp butter in a large pot over medium-high heat.
Add the steak cubes and sear until browned on all sides (about 3-4 minutes per side).
Remove steak from the pot and set aside.
Add the remaining 2 tbsp butter to the pot.
Stir in minced garlic and red pepper flakes, cooking until fragrant (about 30 seconds).
Pour in heavy cream, salt, and pepper, then add the pasta.
Bring to a boil, then reduce heat to a simmer, stirring occasionally.
Let cook until pasta is almost al dente and has absorbed most of the liquid.
Stir in grated Parmesan cheese and chopped parsley.
Return the seared steak to the pot, stirring to combine.
Let cook for another 2-3 minutes, allowing the flavors to blend.
Serve immediately, garnished with extra Parmesan or fresh parsley if desired.
